Corrosive conditions can develop where pipeline sediments accumulate in crude transmission pipelines. The accumulation of sediment at pipeline over bends occurs when inertial forces in the pipe flow cause a thickening in the boundary layer at the pipe floor, which decreases the shear stresses responsible of mobilizing solids. The Shields method has been proposed to predict the accumulation of solid particles taking into account the critical role that shear stress plays in transportation of solids.
The Shields method was originally developed as a river model, a simple dimensionless diagram that can be used to forecast solid particle bed formation in open channels and Newtonian fluid. The model predicts the required minimum viscous shear stress to initiate movement of a particle bed. The dimensionless Shields number provides a ratio of the hydrodynamic drag forces (viscous shear stress) to the net submerged forces of gravity and buoyancy acting on a particle in a loose sediment bed. This meaningful physical number provides useful information about the onset of bed particle movement in pipe flow. The current work explores this dimensionless number, including the applicability domain, to predict particle movement in oil transmission pipelines. Multiple scenarios are considered to compare the model’s prediction to actual pipeline experience.
Particle movement by turbulently flowing fluid is of great importance in a varied range of engineering processes1. During the design of hydraulic transport systems, it is important to estimate the pressure velocity and pressure loss. Commonly the design velocity is selected to minimize pressure losses1. This design velocity might be close to the limit deposit velocity of suspended particles. If the transport velocity is close to the limit deposit velocity, it can cause not only a variety of transport and product quality problems1 but also internal corrosion due to solids accumulation2.
Oil transmission pipelines normally transport petroleum compounds that remain in an incompressible liquid state under normal operating conditions, with solids and water contaminants representing less than 5% by volume2. Two important parameters need to be considered while determining the transport velocity to avoid internal corrosion problems. These parameters are water accumulation and solids accumulation2. Internal corrosion in oil transmission pipelines typically occurs only where water drops out from the hydrocarbon phase and wets the pipe surface2. Therefore, by using flow modelling estimations, it is necessary to analyze critical parameters to predict water drop out and accumulation2. In addition, suspended solids that might accumulate on the pipe surface can contribute to increased internal corrosion issues in locations were waters accumulate2. Thus, transport velocity should be capable not only of preventing water drop out from the liquid phase, but also moving particles to avoid solids deposition. This paper will be focused on studying the particles’ movement and determining critical velocities to ensure particles are transported.
Thermal spraying of zinc and zinc alloys is a well-established process which is used for long-time corrosion protection of steel structures in maritime surrounding conditions and for offshore structures since decades.
The paper summarizes the actual arguments to use long-time cathodic corrosion protection with thermally sprayed zinc and zinc based alloys in different types of surrounding conditions based on detailed laboratory tests, results of long time field tests as well as the monitoring of metalized steel structures in different countries.
The presentation represents best technical and economic performance and a lifetime more than 30 years for thermal spraying with zinc-aluminium 15 for buildings in marine conditions.
In addition it reports about modern process technology, which allows the application of thermal spraying with zinc in factory and at site for new steel structures and for repair work with high quality and near tolerances.
While wind turbines on land are depending on their location often accessible for repairs, choosing a suitable corrosion-protection system for offshore turbines represents a major challenge. Offshore wind turbines face greater corrosive, mechanical and biological stresses than turbines on land 1. In addition, offshore wind turbines are very difficult to access and therefore have much higher maintenance and repair costs 1. For these reasons the corrosion protection has to be very good, long-lasting (>25 years) and fault-tolerant.
The cost of applying the first coating in the plant is € 15-25/m2. A repair outside of the plant but still on land costs around 5 – 10 times more as equipment and personnel have to be transported. If repair work has to be carried out offshore, the costs rise to over € 1000/m2. In experience reports, costs are stated which are 75-100 times 1 higher than the first coating. The main reason for the high offshore repair costs are due to the fact that specially-trained personnel and equipment have to be transported by helicopter or ship to the offshore wind turbines and due to weather conditions only being favourable for short periods. Under the environmental conditions, it is extremely difficult to carry out a competent repair. Figure 5 shows an industrial climber at work on an offshore wind turbine. It is assumed that there are only 40 days a year when weather conditions allow repairs to be carried out. The weather conditions that are required are low humidity, temperatures above the dew point and little wind. A further difficulty lies in getting and keeping the surface to be repaired dry and free of chloride, as the damp, salty air repeatedly contaminates the surface and would therefore reduce the adherence of the coating. In addition, organic repair coatings are applied on multiple layers and setting times have to be heeded between the layers.
Sk, M. Hassan (Qatar University) | Abdullah, A. M. (Qatar University) | Ko, M. (Quest Integrity Group) | Laycock, N. (Qatar Shell GTL) | Ryan, M. P. (Imperial College) | Williams, D. E. (University of Auckland) | Ingham, B. (Callaghan Innovation Lower Hutt)
The effects of micro-alloying of plain carbon steel with Mo (0.7 wt.%) in the presence of 1 wt.% Cr on the corrosion behaviour and scale protectiveness in CO2 saturated (sweet) brine (0.5 M NaCl) environment, under hydrodynamic conditions, at 80°C in a slightly acidic environment (pH 6.6) were investigated. Potentiostatic current transients suggest that there exists a synergistic interaction of Cr and Mo, which induces more rapid scale crystallization compared to the Mo-free steel. The presence of Mo also suppressed the current passing through corrosion scale. SEM images suggested that 1Cr.0.7Mo steel induced formation of thinner scale with better protectiveness compared to their non-Mo counterparts. From the mechanistic perspective, we suggest that the addition of small amounts of Mo induces formation of a crystalline scale at short times and then it accelerates the growth of that crystalline layer, by modifying the local environment at the steel surface. Modeling of this hypothesis is currently in progress.
The development of high durability and low cost materials able to operate in a broad range of increasingly aggressing exposure conditions is critical for the oil and gas industries. Of the practical exposure conditions in the oil-field and pipelines, acidic pH (constituted of aqueous CO2 and/or H2S) and region specific elevated temperatures are common. In these environments scales are typically formed on the surface of the steel - sulfide or carbonate based; these scales can have varying degrees of protectiveness to the steel surface. The steel can potentially be made more durable therefore, by enhancing the formation of a protective, adherent, non-porous crystalline scale on the surface of the corroding steel. This type of protective scale could in principle be encouraged to form by controlling the most important exposure conditions such as pH and temperature: however as temperature is more or less fixed for a particular location, it is hard to find any practically feasible technique of controlling the exposure temperature. However, if one could control local interfacial pH to be modulated at the surface of the steel, thus enabling precipitation of a protective crystalline scale may be induced. One of the most interesting techniques that can be considered for modifying the local pH is micro-alloying: i.e. incorporating small amount of specific element in a base materials in purpose of achieving the desired properties.
High-entropy alloys (HEAs), are multicomponent alloys composed of at least five elements with compositions of 5-35 atomic % for each element. These alloys are being investigated for corrosion protection of natural gas transmission pipelines by studying their behavior under aqueous acidic conditions. Electrochemical and immersion experiments were carried out in 3.5 weight % NaCl solution at pH 4 and 40°C. Oxygen was purged out from the solution by using CO2 as stripping gas. The electrochemical experiments included potentiodynamic and electrochemical impedance spectroscopy tests, used to calculate corrosion rates. Potentiodynamic polarization curves, including cyclic voltammograms, were used to explain active, active-passive, and passive regions of these alloys and susceptibility to localized corrosion. Surface characterization of the corroded samples were performed using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The results of the immersion and electrochemical testing indicate that some of the HEAs have better corrosion performance than commercial alloys UNS N10276, UNS K03014, and UNS 31600.
Research on multicomponent solid solutions in near-equal molar ratio helped to the development of high-entropy alloys (HEAs), a new family of alloys composed of at least five alloying elements with an atomic composition of 5-35 % each. HEAs can also be defined by a configurational entropy of mixing (ΔSconf) of at least 1.5R, where R = 8.314 Jmol-1 K-1 is the gas constant. ΔSconf has the most predominant role on the total mixing entropy, and is calculated using Equation 1 for ideal and regular solutions. This equation is a good representation for liquid alloys and many solid alloys in the melting temperature range. Atomic fraction of element i is described as Xi.1-4
At a greater mixing entropy of an alloy, the formation of single-phase solid solutions is increased and the concentration of intermetallic compounds is minimized.1, 3 High composition of several number of elements offer unique physical and metallurgical aspects with superior mechanical, electrochemical, magnetic characteristics.5
Surface Applied Corrosion Inhibitors (SACI) remain controversial as to effectiveness and the ability to compare materials from different manufacturers and technologies. These materials are liquids applied to the surface of concrete to control the corrosion of embedded reinforcing steel. This presentation will discuss the performance and relative importance of a recent testing program for corrosion inhibition and other performance parameters using documented test methods. The applicability of the tests to evaluate the performance of the material will be described as well as showing comparative data for different generic materials.
Concrete is the second most common man-made material (after potable water) with ~3/4 cubic meter (about 1 cu. yd. or 2 tons) used for every person on the planet per year amounting to more concrete than all other construction materials combined. Construction amounted to $814B of the United States GDP in the first quarter of 2017.1, 2. Based on cement usage figures, of the 82.9 million tons of portland cement and 2.5 million tons of masonry cement produced in the US in 2016 amounting to $10.7 billion, most cement was used to make concrete, worth at least $60 billion. About 70% of cement sales went to ready-mixed concrete producers, 10% to concrete product manufacturers, 9% to contractors (mainly road paving), 4% each to oil and gas-well drillers and to building materials dealers, and 3% to others.3 The American Society of Civil Engineers Report Card estimates $2 trillion is required to just return the infrastructure of the United States to the quality it was in 1988.4 Both the construction industry as well as our infrastructure have significant parts of these estimates relating to concrete usage. It was estimated in 1990 that between $1 and $3 trillion is required to rehabilitate all the reinforced concrete structures suffering from distress.4 Why is concrete so popular? It is inexpensive, versatile, durable, and easily produced from common materials that are not resource constrained (i.e. limestone, silica, iron, aluminum, and gypsum), resistant to fire, flooding, and vermin attack; but concrete is not perfect. The production of cement has been estimated to account for much as 4.5% of global carbon dioxide emissions.5 Concrete has the weaknesses of relatively low tensile strength, brittleness, it is heavy, it absorbs moisture and dissolved chemicals, and deteriorates rapidly in acidic environments. Failure of concrete is usually shown by cracking. Once concrete cracks many of its properties are compromised. Steel reinforcement is added to concrete to improve the tensile properties and although protected (passivated) by the high pH of concrete; it will eventually rust. The protection of steel by concrete is reduced by chloride ion ingress, lowering of the pH through carbonation, and occasionally DC current leakage or dissimilar metal galvanic corrosion. Two universal rules of concrete construction are that concrete cracks and steel rusts.
Most transportation infrastructure is built from steel and concrete. The steel may be in structural sections, such as girders, piles or rails, or embedded in concrete to form reinforced or prestressed concrete. Concrete provides excellent protection for embedded steel because Portland cement is very alkaline, forming a passive, protective layer on the steel surface. Concrete is also permeable, and even good-quality concrete can be penetrated by aggressive chemical ions that may initiate steel corrosion. Migrating corrosion inhibitors (MCIs), a blend of amine carboxylates and amino alcohols, show versatility as admixtures, surface treatments (coatings) and in rehabilitation programs. Examination of the embedded steel rebar after corrosion tests showed no corrosion attack for the MCI treated concrete samples, while non-treated concrete showed localized corrosion. X-ray photoelectron spectroscopy and depth profiling confirmed that the inhibitor had reached the rebar surface in about 150 days. The amine-rich compound on the rebar surface improved corrosion protection for the MCI treated steel rebar even in the presence of chloride ions and prevented red rust formation.
Corrosion is one of the primary concerns in the durability of materials and structures. Research efforts have been made to find a corrosion inhibition process to prolong the life of existing structures and minimize corrosion damage in new structures.1-3 Outside the laboratory environment, infrastructure may suffer from attack by carbonation and chloride. Chloride ions dissolved in water can permeate through the concrete pores, then penetrate the protective oxide film on the steel surface. Carbonation of concrete can lower the amount of chloride ions needed to promote corrosion. In new concrete with a pH of 12-13 about 7,000 to 8,000 ppm chloride is required to initiate steel corrosion. If, however, the pH is lowered to a range of 10 to 11, the chloride threshold for corrosion is significantly lowered to roughly 100 ppm.4
Chlorides in the concrete can come from several sources. They can be cast into the structure by the use of deliberate admixtures (CaCl2), or the chloride ions can appear in the mix (mixing water, aggregates) unknowingly. However, the major cause of chloride-induced corrosion in most structures is the diffusion of chlorides from the environment due to direct exposure with marine environment or the use of deicing salts and chemicals. There are four different mechanisms of chloride transport into crack-free concrete, they include: capillary action, diffusion due to the high concentration on the surface, permeation under pressure, and migration due to electrical potential gradients.4,5 Similar to carbonation, the chloride attack process does not directly corrode steel reinforcement, however, it does break down the protective iron oxide film and promote corrosion. Chlorides do play a role as catalysts to corrosion. However, the mechanism of chloride diffusion into concrete is different for carbonation in that it attacks the passive layer without the requirement of pH reduction.
Cobalt-based alloys, though possessing relevant resistance to oxidation and erosion, inevitably encounter corrosion in acidic environments. In this paper, the cobalt-based alloys containing Cr-Ni-Mo- W-Co ingredients were produced by hot isostatic pressing (HIP) method and their corrosion behavior in hydrochloric acid was investigated using potentiodynamic polarization (PDP) curves, electrochemical impedance spectroscopy (EIS) measurements and immersion corrosion tests. Post-test, the alloys surface was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the ions concentration in corrosion solution was characterized by inductively coupled plasma (ICP). The results indicated that corrosion resistance of three alloys follows the order 3.0Mo > 1.0Mo > 0.5Mo. During corrosion process, constituent Ni, Fe, Cr and Co in base material tend to dissolve preferentially, while carbides precipitates will be protected due to galvanic coupling in hydrochloric acid solution. Different alloy constituents and microstructures will result in different corrosion behaviors.
Owing to the high hardness and good toughness over a wide temperature range, cobalt-based alloys present excellent wear resistance and valued industrial applications, such as cutting tools or structural materials at high temperature . However, they do not show desirable corrosion resistance in harsh corrosive environment. Undergoing corrosion usually deteriorates the surface properties and wear resistance of a tool in service, accelerating its failure . Therefore, it is greatly valued to improve its corrosion resistance and select appropriate materials for service in harsh environment.
The corrosion properties of WC-Co hard-metals received great concern from researchers . A.M. Human etc. have investigated the electrochemical behavior of tungsten carbide based cemented carbides, found that the binder corrodes faster than the carbide and is leached out in spite of exhibiting a pseudopassive behavior . Sutha Sutthiruangwong etc. have examined the corrosion properties of cemented carbides with cobalt binder phase in HCl and H2SO4 solution, found the corrosion resistance of cemented carbide increases with decreasing magnetic saturation, and lower cobalt binder content exhibits better corrosion resistance . S. Hochstrasser etc. have carried a systematic investigation on the corrosion mechanisms of the WC-Co composite in solutions with different pH, they found that the solution pH plays more dominant role on corrosion susceptibility than the specific ions. The corrosion process of WC-Co consists mainly of Co dissolution in neutral and acidic solution, while WC dissolution becomes more significant at alkaline pH . The grain size of WC-10Co alloy influences its electrochemical corrosion behaviors, the alloys with smaller WC grain sizes exhibit better corrosion resistances in solutions of NaOH and Na2SO4, while the alloys with larger WC grain sizes exhibit better corrosion resistance in H2SO4 .
The influence of ferrite and heat treatment condition on the toughness of ASTM(1) A 351 Grade CF3M (0.03C-19Cr-9Ni-2Mo) and CF8M (0.08C-19Cr-9Ni-2Mo) castings used in valve bodies in both Cold -200F BACKGROUND ExxonMobil(2) completed a study of the influence of ferrite and heat treatment condition on the toughness of ASTM A 351 Grade CF3M (0.03C-19Cr-9Ni-2Mo) and CF8M (0.08C-19Cr-9Ni-2Mo) castings used in valve bodies in both Cold -200F
ExxonMobil(2) completed a study of the influence of ferrite and heat treatment condition on the toughness of ASTM A 351 Grade CF3M (0.03C-19Cr-9Ni-2Mo) and CF8M (0.08C-19Cr-9Ni-2Mo) castings used in valve bodies in both Cold -200F
In order to make risk-informed decisions when designing corrosion mitigation and remediation programs for lateral piping, consequence and likelihood of a failure (LoF) are required to estimate the risk. Within industry, lateral piping does not always have In-Line Inspection (ILI) or Direct Assessment (DA) data. As such, the LoF models for corrosion on uninspected lateral piping rely on a semiquantitative historic-based approach. This approach leverages a historic failure rate and modification factors to provide a lateral-specific rate of failure (Rf). However, when lateral piping has been inspected, a quantitative assessment can be applied to evaluate LoF. Based on a sample assessment on laterals with inspection data, the historic-based model showed more conservative LoF results. This conservatism could potentially drive unnecessary mitigation or remediation work on lateral piping where inspection data may not be available. This paper considers the use of calibration of the historic-based model with the inspection data available to provide a less conservative and more accurate assessment of the likelihood of failure for lateral piping without inspection data. Given the limitations and constraints in the data and models, it proposes the use of risk-informed decision making to develop the integrity management plan.
Managing the corrosion threat on lateral piping can be a challenge due to limited inspection capabilities and uncertainties in the available data. Lateral piping does not always have In-Line Inspection (ILI) or Direct Assessment (DA) data, so the data used in probability of failure (PoF) analysis is not always available. Therefore, a likelihood of failure (LoF) is estimated using a semi-quantitative historic-based rate of failure (Rf) approach . This approach leverages a historic failure rate and modification factors to provide a lateral-specific rate of failure (Rf). Within this case study, a sample evaluation of PoF and Rf is completed on 10 laterals. The Rf estimates are generally conservative compared to the PoFs but do not directly align. This conservatism and uncertainty could potentially drive unnecessary inspection and mitigation work on lateral piping.
Klenke, Karola (BGH Edelstahl Siegen GmbH) | Bosch, Christoph (Salzgitter Mannesmann Forschung GmbH) | Müller, Marc André (BGH Edelstahlwerke GmbH) | Müller, Michael (BGH Edelstahl Siegen GmbH) | Hippenstiel, Frank (BGH Edelstahl Siegen GmbH)
13Cr Super Martensitic Stainless Steel (SMSS) with a specified minimum yield (SMYS) of 110 ksi is commonly used in the Oil & Gas industry.
The present work has been aimed at evaluating the influence of different heat treatment processes on the corrosion resistance of 110 ksi 13Cr SMSS. Bars were produced with a conventional Qt process in gas fired batch furnaces as well as on an integrated forging line with inductive re-heating and direct quenching. The bars were tested according to NACE TM0177 Method A to prove the resistance to SSC. Tests were performed in several environments with different Chloride concentrations, pH levels and H2S partial pressures from 0.01 up to 0.05 bar. First results confirm the potential of new production concepts for SMSS steel bar products.
Due to the combination of high strength and corrosions resistance 13Cr Super Martensitic Stainless Steels (SMSS) with specified minimum yield strength (SMYS) of 110 ksi are used commonly in the Oil & Gas industry. In NACE MR0175 / ISO 15156-3 1 only 13Cr SMSS (UNS (1) S41425, UNS S41426 and UNS S41427) at hardness levels corresponding to 95 ksi specified minimum yield strength (SMYS) are covered. Nevertheless, there is a regular demand for 13Cr SMSS with minimum 110 ksi yield strength from the Oil & Gas industry.
In 2005 the sulfide stress cracking (SSC) resistance of forged 13Cr SMSS 110 ksi bar stock under different chloride concentration, pH and H2S partial pressure was published. Application limits for this material were defined. 2
Further trials with increasing chloride concentrations but lower pH were done with 13Cr OCTG tubing material. The ‘no SSC’ domain for 110 ksi grade super 13Cr steel (UNS 41426) has been proposed as a function of Cl- concentration, pH and H2S partial pressure. The influence of Cl- concentration was larger for the lower pH or for the higher H2S partial pressure environments. 3